The document provides information on writing business letters and the differences between formal and informal writing styles. It discusses that business letters should be written in a formal style using clear, concise, complete, constructive and correct language. Formal writing tends to use complex sentences, an objective tone, full words and contractions while informal writing has a colloquial and simple style using contractions and abbreviations. The document also outlines common grammar issues to avoid such as fragments, comma splices, run-on sentences and dangling participles.